Integrated circuit comprising voltage modulation circuitry and method therefor

ABSTRACT

An integrated circuit comprising voltage modulation circuitry arranged to convert an input voltage level at an input node to an output voltage level at an output node. The voltage modulation circuitry comprises a switching element arranged to connect the input node to the output node when in an ON condition, and switching control module operably coupled to the switching element and arranged to control the connection of the input node to the output node by the switching element in accordance with a switching frequency. The voltage modulation circuitry further comprises frequency control module operably coupled to the switching control module and arranged to receive an indication of the input voltage level at the input node, and to configure the switching frequency based at least partly on the input voltage level indication.

FIELD OF THE INVENTION

The field of this invention relates to an integrated circuit comprisingvoltage modulation circuitry and a method therefor. More particularly,the field of this invention relates to an integrated circuit comprisingvoltage modulation circuitry arranged to convert an input voltage levelat an input node to an output voltage level at an output node, and amethod therefor.

BACKGROUND OF THE INVENTION

The use of DC to DC converters for converting a source of direct current(DC) from one voltage level, for example as supplied by a battery, to aanother voltage level, for example as required by a particularelectronic circuit, is well known. In particular, switch-mode DC to DCconverters are well known that convert one DC voltage level to anotherby storing energy temporarily, and then releasing the stored energy tothe output at a different voltage level. The storage of the energy maybe in either magnetic field storage components (e.g. inductors,transformers, etc.) or electric field storage components (e.g.capacitors). Such switch-mode DC to DC conversion is more powerefficient than linear voltage regulation, and thus switch-mode DC to DCconverters are typically more suitable for use within battery operateddevices.

Within the automotive industry, DC to DC converters are used to convert,for example, a first voltage level supplied by the vehicle battery to asecond voltage level required by one or more electronic componentsoperating within the vehicle. Such DC to DC converters are required tobe able to cope with a wide input voltage range due to variations in thevoltage supplied by the battery, as well as transient voltages that maybe experienced, for example as a result of a ‘load dump’. A load dumpmay occur, for example, upon the disconnection of the vehicle batteryfrom the alternator while the battery is being charged. As a result ofsuch a disconnection, other loads connected to the alternator (e.g. theDC to DC converter) may experience a power surge resulting in asignificantly increased voltage level. Thus, a typical input voltagerange that such a DC to DC converter is required to operate across maybe, say, between 5 v and 40 v.

The requirements for the next generation of single board computers(SBCs), such as are used within the automotive industry, are currentlybeing defined. In particular, these requirements include severalrequirements that affect DC to DC converter performance needs when usedwithin the SBCs. Such requirements for the DC to DC converters include:maximum power dissipation; overall efficiency, dynamic response, outputvoltage ripple, etc.

Known DC to DC converters use various control methods, such as PulseFrequency Modulation (PFM), Pulse Burst Modulation (PBM), Pulse WidthModulation (PWM), etc. For example, in the case of PWM mode control, aswitching frequency for, say, a MOSFET (Metal Oxide Semiconductor FieldEffect Transistor) of the DC to DC converter is fixed, whilst the dutycycle is adjusted through a feedback loop. The power dissipation withinthe switching MOSFET may be expressed as:

-   -   (a) Conduction losses, which are primarily dependent upon the        ‘ON’ resistance of the MOSFET, the duty cycle and the load        current; and    -   (b) Switching losses, which are primarily dependent upon the        input voltage, switching frequency and the load current.

When such a DC to DC converter experiences a high input voltage, forexample as caused by a load dump, the switching power losses increasesignificantly, requiring the device to be able to dissipate the powerlost as, for example, heat. In order to achieve this, the externalcomponent of the DC to DC converter must be suitably sized in order tobe able to sufficiently dissipate this heat. However, size constraintsdue to available space, costs, etc, and also the maximum powerdissipation and overall efficiency requirements being proposed for thenext generation of SBCs, mean that such DC to DC converters areconstrained in how they are able to cope with the power losses caused bysuch high input voltages.

In order to reduce the switching losses during periods of high inputvoltage, it is necessary to decrease the switching frequency of the DCto DC converter. However, this results in a significant degradation inthe dynamic response of the DC to DC converter, and an increase in theoutput voltage ripple. Such degradation in the dynamic response andincrease in the output voltage ripple are not only detrimental to theperformance of the DC to DC converter, but also conflict with theability of the DC to DC converter to comply with the proposedrequirements for the next generation of SBCs.

SUMMARY OF THE INVENTION

The present invention provides an integrated circuit comprising voltagemodulation circuitry, an electronic system comprising such an integratedcircuit and a method therefor as described in the accompanying claims.

Specific embodiments of the invention are set forth in the dependentclaims.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, aspects and embodiments of the invention will bedescribed, by way of example only, with reference to the drawings.Elements in the figures are illustrated for simplicity and clarity andhave not necessarily been drawn to scale.

FIG. 1 illustrates an example of an integrated circuit comprisingvoltage modulation circuitry.

FIG. 2 illustrates an example of an electronic system comprising theintegrated circuit of FIG. 1.

FIG. 3 illustrates a graph showing an example of switching losses.

FIG. 4 illustrates a graph showing an example of output voltage ripple.

FIG. 5 illustrates a graph showing an example of efficiency.

FIG. 6 illustrates a simplified flowchart of an example of a method forconverting an input voltage level at an input node to an output voltagelevel at an output node.

DETAILED DESCRIPTION

The invention will now be described, by way of example, in terms of anintegrated circuit (IC) comprising a DC to DC converter forming part ofan electronic system, such as a single board computer (SBC) devicesuitable for use within the automotive industry. However, the exampleshereinafter described are equally applicable to other electronic systemsand devices, and in particular applicable to alternative voltagemodulation circuitry arrangements and alternative electronic devices.Furthermore, because the apparatus implementing the present inventionis, for the most part, composed of electronic components and circuitsknown to those skilled in the art, circuit details will not be explainedin any greater extent than that considered necessary, as illustratedbelow, for the understanding and appreciation of the underlying conceptsof the present invention and in order not to obfuscate or distract fromthe teachings of the present invention.

Referring now to FIG. 1, there is illustrated an example of an IC 105comprising voltage modulation circuitry, generally indicated as 100,arranged to convert an input voltage level at an input node 110 to adifferent output voltage level at an output node 115. In particular forthe illustrated example, the input voltage at the input node 110 isprovided by a power source 170 such as a battery, and the output voltageat the output node 115 is supplied to a load 175. The IC 105 may bearranged to form part of an electronic system such as a single boardcomputer (SBC) as illustrated generally at 200 in FIG. 2. For theexample illustrated in FIG. 2, the voltage modulation circuitry 100 ofthe IC 105 is arranged to convert an input voltage level provided bypower source 170 at input node 110 to an output voltage level suppliedto a load 175 at an output node 115, the load for the exampleillustrated in FIG. 2 comprising a plurality of system elementsillustrated generally at 210.

Referring back to FIG. 1, the voltage modulation circuitry 100 comprisesa switching element 120 arranged to connect the input node 110 to theoutput node when the switching element 120 is in an ‘ON’ condition, andsubsequently release the stored energy when the switching element 120 isin an ‘ON’ condition. For the illustrated example, the voltagemodulation circuitry 100 is based on a buck converter configuration, andin particular comprises a switching element 120 in a form of a MOSFET(Metal Oxide Semiconductor Field Effect Transistor) operably coupledbetween the input node 110 and the output node 115, and energy storagecircuitry operably coupled in series with the switching element 120,between the switching element 120 and the output node 115. For theillustrated example, the energy storage circuitry comprises an inductor190 operably coupled in series with the switching element 120, andcapacitor 195 operably coupled between the output node 115 and ground. Adiode 197 is provided between ground and the connection between theswitching element 120 and the inductor 190 such that, when the switchingelement is in an ‘OFF’ state and energy is stored within inductor 190,the diode 197 becomes forward biased, thereby allowing current to flowthrough the diode 190. Alternative energy storage components may beprovided, for example comprising any suitable combination of one or moreof an inductor, a transformer, a capacitor, etc. In this manner, theenergy storage components 190, 195 and the diode 197 are able totemporarily store energy from the input node when the switching element120 is in an ‘ON’ condition, and subsequently release the stored energywhen the switching element 120 is in an ‘OFF’ condition, resulting in asubstantially uninterrupted but lower averaged voltage level at theoutput node 115 as compared to that at the input node 110. Accordingly,the voltage modulation circuitry 100 is arranged to provide switch modevoltage modulation between the input node 110 and the output node 115.Whilst for the illustrated example, the energy storage components areintegrated within the IC 105, in other examples the energy storagecomponents may alternatively, or additionally, be provided external toan IC that comprises the voltage modulation circuitry.

In this example, the voltage modulation circuitry 100 further comprisesswitching control module 125 operably coupled to the switching element120 and arranged to control the connection of the input node 110 to theoutput node 115 by the switching element 120 in accordance with aswitching frequency. For the illustrated example, the switching controlmodule 125 is arranged to regulate the connection of the input node 110to the output node 115 by the switching element 120 in accordance with aswitching frequency signal 145 received from oscillator circuitry 140.More particularly, for the illustrated example, the switching controlmodule 125 comprises an SR flip-flop arranged to receive as a ‘set’signal the switching frequency signal 145. The switching control module125 may be arranged to use any suitable control method to regulate theconnection of the input node 110 to the output node 115 by the switchingelement 120, such as Pulse Frequency Modulation (PFM), Pulse BurstModulation (PBM), Pulse Width Modulation (PWM) etc. For example, in thecase of PWM mode control, the switching frequency for the switchingelement 120 may be substantially regular, whilst a duty cycle for theswitching of the switching element 120 may be adjusted through afeedback loop, as described in greater detail below.

The voltage modulation circuitry 100 of FIG. 1 further comprisesfrequency control module 130 arranged to receive an indication 132 ofthe input voltage level at the input node 110, and to configure theswitching frequency based at least partly on the input voltage levelindication provided in path 132. In this manner, the switching frequencyin accordance with which the switching control circuitry 125 controlsthe switching element 120 may be adjusted to take into considerationvariations in the input voltage level at the input node 110. Inparticular, the frequency control module 130 may be arranged to adaptthe switching frequency to compensate for transient voltages that may beexperienced, for example due to ‘load dump’ or the like. For example,within the automotive industry, a load dump may occur upon thedisconnection of a vehicle battery from an alternator while the batteryis being charged. As a result of such a disconnection, other loadsconnected to the alternator, such as voltage modulation circuitry 100,may experience a power surge resulting in a significantly increasedinput voltage level.

For the example illustrated in FIG. 1, the frequency control module 130is further arranged to compare an input reference value 136 based on theinput voltage level indication 132 to one or more threshold values inorder to determine an appropriate switching frequency value. Thefrequency control module 130 may then configure the switching frequencyin accordance with the determined switching frequency value.Accordingly, for the illustrated example, the frequency control module130 comprises a memory element 135, for example comprising one or moreregisters, in which the one or more threshold values may be stored. Thefrequency control module 130 further comprises comparison module 137arranged to compare the input reference value 136 to the one or morethreshold values stored within memory element 135. In particular for theillustrated example, the comparison module 137 is arranged to output afrequency control signal 138 to the oscillator circuitry 140, wherebythe oscillator circuitry 140 is arranged to generate the switchingfrequency signal 145 in accordance with the received frequency controlsignal 138.

In this manner, at least a first threshold value may be configuredwithin the memory element 135 such that the input reference value 136 islikely to be less than this first threshold value during normaloperating conditions when the input voltage level is within a firstvoltage range, for example between 0 v and 20 v. Accordingly, uponcomparison of the input reference value 136 to this first thresholdvalue by the comparison module 137, if the input reference value 136 isless than this first threshold value, the comparison module 137 may bearranged to cause the oscillator circuitry 140 to generate a switchingfrequency signal 145 comprising a first switching frequency. Conversely,if the input reference value 136 is greater than this first thresholdvalue, the comparison module 137 may be arranged to cause the oscillatorcircuitry 140 to generate a switching frequency signal 145 comprising asecond, reduced switching frequency.

Thus, when the input voltage level rises above this first voltage range(and therefore threshold) associated with normal operating conditions,for example as a result of a load dump or the like, the switchingfrequency is reduced. In this manner, the switching losses of thevoltage modulation circuitry may be reduced during periods of high inputvoltage levels, and thus the amount of power needed to be dissipatedduring such periods, for example as heat, is also reduced. Accordingly,the size requirements for an external component (not shown) of the IC105 in order to be able to sufficiently dissipate this heat is alsoreduced as well as supporting a reduction in the maximum powerdissipation and overall efficiency to meet the requirements beingproposed for the next generation of SBCs. Furthermore, since under suchnormal operating conditions, when the input voltage level is containedwithin this first voltage range, the higher switching frequency isconfigured. As a result, degradation in the dynamic response of thevoltage modulation circuitry 100 and an increase in the output voltageripple therefor, caused by decreasing the switching frequency may besubstantially avoided under such normal operating conditions. Thisimproves the performance of the voltage modulation circuitry 100 undersuch normal operating conditions, and enables the voltage modulationcircuitry 100 to comply with the proposed requirements for the nextgeneration of SBCs during such normal operating conditions. Sinceoperating conditions that result in the input voltage level rising abovethis first voltage range, into what comprises an atypically extendedvoltage range, may be considered as abnormal, slight degradation in thedynamic response and increase in the output voltage ripple caused by thetemporary reduction in the switching frequency during such abnormaloperating conditions is typically an acceptable trade off for reducingthe switching losses.

In one example, more than one threshold value may be configured withinthe memory element 135. For example, a second threshold value may beconfigured within the memory element 135 such that the input referencevalue 136 is likely to be greater than this second threshold valueduring excessive operating conditions when the input voltage level isabove a different value, for example above 40 v. Accordingly, uponcomparison of the input reference value 136 to the first threshold value(discussed above) by the comparison module 137, if the input referencevalue 136 is determined as being greater than the first threshold value,the comparison module 137 may then compare the input reference value 136to the second threshold value. If the input reference value 136 is lessthan the second threshold value, the comparison module 137 may then bearranged to cause the oscillator circuitry 140 to generate a switchingfrequency signal 145 comprising a second reduced switching frequency.Conversely, if the input reference value 136 is also greater that thesecond threshold value, the comparison module 137 may be arranged tocause the oscillator circuitry 140 to generate a switching frequencysignal 145 comprising a third, further reduced switching frequency. Inthis manner, a more gradual trade off between (a) power loss andefficiency; and (b) dynamic response and output voltage ripple, may beachieved.

By way of example, the oscillator circuitry 140 may be arranged togenerate a default switching frequency (f_(s)). The comparison module137 may be arranged to provide a modifier value to the oscillatorcircuitry 140 via the frequency control signal 138 depending on theresult of the comparison of the input reference value 136 to the one ormore threshold values. Accordingly, when the comparison module 137 isrequired to cause the oscillator circuitry 140 to generate a switchingfrequency signal 145 comprising a first switching frequency (say, foruse during normal operating conditions), the comparison module 137 mayoutput a modifier value of, say, ‘1’. The oscillator circuitry 140 mayaccordingly be arranged to divide the default switching frequency bythis value, and output the resulting signal as the switching frequencysignal 145. Thus, the first switching frequency in this scenariocomprises the default switching frequency (f_(s)).

Conversely, when the comparison module 137 is required to cause theoscillator circuitry 140 to generate a switching frequency signal 145that comprises a second, reduced switching frequency, the comparisonmodule 137 may output a modifier value of, say, ‘2’. Accordingly, theoscillator circuitry 140 divides the default switching frequency by thisvalue, and outputs the resulting signal as the switching frequencysignal 145. Thus, the second switching frequency in this scenariocomprises half the default switching frequency (f_(s)/2). Similarly,when the comparison module 137 is required to cause the oscillatorcircuitry 140 to generate a switching frequency signal 145 thatcomprises a third, further reduced switching frequency, the comparisonmodule 137 may output a modifier value of, say, ‘4’. Accordingly, theoscillator circuitry 140 divides the default switching frequency by thisvalue, and outputs the resulting signal as the switching frequencysignal 145. Thus, the third switching frequency in this scenariocomprises a quarter of the default switching frequency (f_(s)/4).

In one example, the memory element 135 may be configurable by, forexample, a signal processing unit (not shown) or the like within theelectronic system 200 of FIG. 2 of which the IC 105 forms a part. Inthis manner, the threshold values may be configurable by way ofapplication code being executed by said signal processing unit, forexample during a boot up sequence, or during system configurationinstigated externally via, say, a debug port (not shown) or the like.Furthermore, although the use of one and two threshold values have beendescribed in the above examples, in other examples any suitable numberof threshold values may be used, with more threshold values enabling agreater granularity of switching frequencies to be available, thusenabling greater granularity in the trade off between (a) power loss andefficiency; and (b) dynamic response and output voltage ripple.

Referring back to FIG. 1, the frequency control module 130 of theillustrated example is further arranged to receive an indication 134 ofa load current, and to combine the input voltage level indication 132and the load current indication 134 to generate the input referencevalue 136 such that the input reference value 136 comprises an inputpower reference value. For the example illustrated in FIG. 1, the loadcurrent indication 134 is provided by detecting a potential differenceacross a resistance 173 within the load current path. Accordingly, forthe illustrated example, the frequency control module 130 is arranged toconfigure the switching frequency based not just on the input voltagelevel indication 132, but also on the load current indication 134. Inparticular for the illustrated example, the frequency control module 130comprises multiplication module 133 arranged to multiply the inputvoltage level indication 132 and the load current indication 134together to generate the input reference value 136. In this manner, theinput reference value 136 comprises an indication of the input power forthe voltage modulation circuitry 100. Thus, for the illustrated examplethe frequency control module 130 is arranged to configure the switchingfrequency based on an indication of the input power for the voltagemodulation circuitry 100.

The switching control module 125 of the illustrated example is arrangedto receive a duty cycle signal 150, and to further regulate theconnection of the input node 110 to the output node 115 by the switchingelement 120 in accordance with the duty cycle signal 150, in addition tothe switching frequency signal 145. More particularly for theillustrated example, the switching control module 125, which comprisesan SR flip-flop, is arranged to receive as a ‘reset’ signal the dutycycle signal 150. Thus, for the illustrated example, the switchingcontrol module 125 may be arranged to regulate the switching element 120using pulse width modulation (PWM) mode control, whereby the switchingfrequency for the switching element 120 may be substantially regular,whilst a duty cycle may be adjusted in accordance with the duty cyclesignal 150. For the illustrated example, the duty cycle signal 150 isgenerated by comparison module 155 based on a comparison between theload current indication 134 and a voltage feedback signal 160, which forthe illustrated example is generated based on a difference between anindication 185 of the output voltage level at the output node 115 and avoltage reference signal 180. In this manner, the voltage feedbacksignal 160, and thereby the duty cycle signal 150 are dynamicallydependent on the difference between the output voltage level indication185 at the output node 115 and the voltage reference signal 180.

In particular for the illustrated example, when the output voltage levelindication 185 is less than the voltage reference signal 180 value, thusindicating that the output voltage level at the output node 115 is belowa specific voltage level, the resulting voltage feedback signal 160indicates by how much the output voltage level indication 185 is belowthe voltage reference signal 180. Assuming this indication of by howmuch the output voltage level indication 185 is below the voltagereference signal 180 is greater than the load current indication 134,the comparison module 155 generates a duty cycle signal 150 that causesthe switching control module 125 to turn the switching element 120 ‘ON’at the start of the next switching frequency cycle. As a result, uponthe switching element 120 being turned ‘ON’ at the start of the nextswitching frequency cycle, the output node 115 is connected to the inputnode 110 (via the energy storage components), thereby causing thevoltage level at the output node 115 to increase. When the voltage levelat the output node 115 rises above the specific voltage level mentionedabove, the output voltage level indication 185 will exceed the value ofthe voltage reference signal 180. As a result, the voltage feedbacksignal 160 provides an indication to the comparison module 155 that theoutput voltage level indication 185 exceeds the voltage reference signal185 value, and by how much. Assuming this indication is less than theload current indication 134, the comparison module 155 generates a dutycycle signal 150 to cause the switching control module 125 to turn theswitching element 120 ‘OFF’. As a result, upon the switching elementbeing turned ‘OFF’, the output node 115 is disconnected from the inputnode 110 such that the current (energy) provided to the output node 115is supplied by the energy storage components 190, 195, 197, therebyresulting in a gradual decrease in the voltage level at the output node115, as the energy stored within the energy storage components 190, 195,197 diminishes.

In this manner, the duty cycle of the voltage modulation circuitry 100is dynamically adjusted in order to substantially maintain an averagevoltage level at the output node 115, dependent upon the voltagereference signal 180. Thus, when the frequency control module 130 causesthe switching frequency to be changed, for example to compensate for aload dump or the like, the duty cycle is dynamically adjusted tocomplement the change in the switching frequency, in order to maintainsubstantially the same average voltage level at the output node 115.

In accordance with some examples, the comparison module 137 may comprisean hysteretic comparator. In this manner, oscillating between switchingfrequencies caused by the input reference value 136 being close to athreshold value may be substantially avoided.

Referring now to FIG. 3 there is illustrated a graph 300 showing anexample of switching losses against input voltage multiplied by loadcurrent (Vin*lload) for a known voltage modulation circuit and for acomparable voltage modulation circuit adapted in accordance with anexample of the present invention. In particular, the graph 300 shows afirst plot 310 illustrating the switching losses plotted againstVin*lload for a voltage modulation circuit that is arranged to useconventional pulse width modulation (PWM). The graph 300 further shows asecond plot 320 illustrating switching losses Vin*lload for a voltagemodulation circuit adapted in accordance with an example of the presentinvention, such as the voltage modulation circuit 100 of FIG. 1.

For lower values of Vin*lload, for example representative of normaloperating conditions, the two plots 310, 320 follow substantially thesame curve, since the switching frequency and duty cycle for each of thevoltage modulation circuits is configured for achieving good dynamicresponse and output voltage ripple characteristics of the respectivevoltage modulation circuits under such conditions. As can be seen, asthe Vin*lload value increases so do the switching losses, therebyrequiring the external components comprising the respective voltagemodulation circuits to dissipate more and more power in the form ofheat. As illustrated by plot 310, the switching losses for the voltagemodulation circuitry that uses conventional pulse width modulationcontinue to increase substantially indefinitely as Vin*lload increases,thereby requiring the external component comprising the conventionalvoltage modulation circuitry to be sized adequately to cope with suchpower dissipation requirements.

However, for the voltage modulation circuitry adapted in accordance withan example of the present invention, when Vin*lload reaches a thresholdvalue, indicated generally by arrow 330, the switching frequency isreduced as described above. As a result, the switching losses alsodecrease, as illustrated by plot 320. Accordingly, the amount of powerrequired to be dissipated by the external component comprising thevoltage modulation circuitry adapted in accordance with examples of thepresent invention is significantly reduced, thus enabling the sizingthereof to be significantly reduced. Such a reduction may be in theorder of 5% as compared with voltage modulation circuits usingconventional pulse width modulation.

Referring now to FIG. 4, there is illustrated a graph 400 showing anexample of output voltage ripple plotted against input voltagemultiplied by load current (Vin*lload) for known voltage modulationcircuits and for a comparable voltage modulation circuit adapted inaccordance with an example of the present invention. In particular, thegraph 400 shows four plots 410, 420, 430, 440. The first plot 410illustrates the output voltage ripple against Vin*lload for a firstvoltage modulation circuit arranged to use conventional PWM comprising afixed switching frequency of 300 kHz, and comprising an energy storagecomponent in a form of a 47 μH inductor. The second plot 420 illustratesthe output voltage ripple plotted against Vin*lload for a second voltagemodulation circuit arranged to use conventional PWM comprising a fixedswitching frequency of 150 kHz, and comprising an energy storagecomponent in a form of a 47 μH inductor. The third plot 430 illustratesthe output voltage ripple plotted against Vin*lload for a third voltagemodulation circuit arranged to use conventional PWM comprising a fixedswitching frequency of 150 kHz, and comprising an energy storagecomponent in the form of a 90 μH inductor. The fourth plot 440illustrates the output voltage ripple plotted against Vin*lload for afourth voltage modulation circuit adapted in accordance with an exampleof the present invention, and comprising an adaptable switchingfrequency, and comprising an energy storage component in the form of a47 μH inductor.

As illustrated by plot 420, the use of a relatively low switchingfrequency of 150 kHz with a relatively low value inductor of 47 μHresults in an undesirably high output voltage ripple. In order to avoidsuch a high output voltage ripple using conventional voltage modulationcircuits, either the switching voltage may be increased, for example asillustrated at 300 kHz by plot 410, or the inductance value may beincreased, for example as illustrated at 90 μH by plot 430.

A problem with increasing the switching frequency is that it increasesthe switching losses, particularly when high input voltages areexperienced, such as due to a load dump or the like. As a result, anincrease in the switching frequency requires an increase in the amountof heat dissipation, which in turn requires an increase in the size ofthe external component for the voltage modulation circuitry.Accordingly, increasing the switching frequency is undesirable.

Whilst increasing the inductance value avoids the need for increasingthe switching frequency, the increased inductance significantly reducesthe efficiency of the voltage modulation circuitry (as illustrated inFIG. 5 and described in greater detail below).

For the voltage modulation circuitry adapted in accordance with thepresent invention, represented by plot 440, for lower values ofVin*lload, the switching frequency may be configured to a relativelyhigh value, for example 300 kHz. In this manner, the output voltageripple remains sufficiently low for good performance, whilst alsoallowing an acceptably low inductance value, thereby providing goodvoltage conversion efficiency. However, when Vin*lload reaches athreshold value, indicated generally by arrow 450, the switchingfrequency is reduced, as described above, for example to 150 kHz. Inthis manner, significant increases in switching losses caused by highinput voltages and high switching frequencies may be avoided. Althoughsuch a decrease in the switching frequency causes an increase in theoutput voltage ripple as illustrated by plot 440, because the operatingconditions resulting in Vin*lload rising above the threshold value maytypically be abnormal, such temporary degradation in terms of outputvoltage ripple is generally perceived as an acceptable trade off.

Referring now to FIG. 5, there is illustrated a graph 500 showing anexample of efficiency plotted against input voltage multiplied by loadcurrent (Vin*lload) for a known voltage modulation circuit and for acomparable voltage modulation circuit adapted in accordance with anexample of the present invention. In particular, the graph 500 shows afirst plot 510 illustrating the efficiency plotted against Vin*lload fora voltage modulation circuit arranged to use conventional PWM comprisinga fixed switching frequency 150 kHz, and comprising an energy storagecomponent in a form of a 90 μH inductor. The graph 500 further shows asecond plot 520 illustrating the efficiency plotted against Vin*lloadfor a voltage modulation circuit adapted in accordance with an exampleof the present invention, and comprising an adaptable switchingfrequency, and comprising an energy storage component in the form of a47 μH inductor.

As previously mentioned with reference to plot 430 of FIG. 4, a problemwith a high inductance value of, in this example, 90 μH and the lowerswitching frequency of, in this example, 150 kHz for the conventionalvoltage modulation circuit represented by plot 510 is that the highinductance and low switching frequency results in a relatively poorefficiency performance of the voltage modulation circuitry, asillustrated by plot 510. However, for the voltage modulation circuitryadapted in accordance with the present invention, represented by plot520, for lower values of Vin*lload, the switching frequency may beconfigured to a relatively high value, for example 300 kHz. In thismanner, the higher switching frequency and lower inductance valueresults in relatively high efficiency. When Vin*lload reaches athreshold value, indicated generally by arrow 530, the switchingfrequency is reduced, as described above, for example to 150 kHz, inorder to avoid significant increases in switching losses caused by highinput voltages and high switching frequencies. Although such a decreasein the switching frequency causes a decrease in the output efficiency ofthe voltage modulation circuitry as illustrated by plot 520, because theoperating conditions resulting in Vin*lload rising above the thresholdvalue may typically be abnormal, such temporary degradation in terms ofefficiency is generally perceived as an acceptable trade off.

Thus, and as illustrated by the graphs of FIG's 3 to 5, a voltagemodulation circuit adapted in accordance with an example of the presentinvention is able to achieve good performance in terms of efficiency,output voltage ripple and dynamic response for lower input voltagelevels, whilst reducing the switching losses resulting from higher inputvoltage levels, and thereby reducing the amount of power that isrequired to be dissipated, for example as heat. Furthermore, the voltagemodulation circuit adapted in accordance with an example of theinvention requires a reduced size of the external component for thevoltage modulation circuit.

Referring now to FIG. 6, there is illustrated a simplified flowchart 600of an example of a method for converting an input voltage level at aninput node to an output voltage level at an output node, for example asmay be implemented by a voltage regulation circuit, such as a DC to DCconverter or the like. The method starts at step 610, and moves to step620 with the receipt of an indication of the input voltage level at theinput node 620. For the illustrated example, the method then comprisesreceiving a load current indication a shown in step 630. Next, in step640, an input reference value is generated by combining the receivedinput voltage indication and load current indication. The inputreference value is then compared with one or more threshold values todetermine an appropriate switching frequency value, in step 650. Aswitching frequency is then configured in accordance with the determinedswitching frequency value in step 660, and a connection of the inputnode to the output node is then regulated in accordance with theconfigured switching frequency in step 670.

In the foregoing specification, the invention has been described withreference to specific examples of embodiments of the invention. It will,however, be evident that various modifications and changes may be madetherein without departing from the broader scope of the invention as setforth in the appended claims. For example, the connections may be anytype of connection suitable to transfer signals from or to therespective nodes, units or devices, for example via intermediatedevices. Accordingly, unless implied or stated otherwise the connectionsmay for example be direct connections or indirect connections.

Because the apparatus implementing the present invention is, for themost part, composed of electronic components and circuits known to thoseskilled in the art, circuit details will not be explained in any greaterextent than that considered necessary as illustrated above, for theunderstanding and appreciation of the underlying concepts of the presentinvention and in order not to obfuscate or distract from the teachingsof the present invention.

Although the invention may have been described with respect to specificconductivity types or polarity of potentials, skilled artisansappreciated that conductivity types and polarities of potentials may bereversed.

It is to be understood that the architectures depicted herein are merelyexemplary, and that in fact many other architectures can be implementedwhich achieve the same functionality. In an abstract, but still definitesense, any arrangement of components to achieve the same functionalityis effectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermediary components. Likewise, any two componentsso associated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the functionality of the above described operations merelyillustrative. The functionality of multiple operations may be combinedinto a single operation, and/or the functionality of a single operationmay be distributed in additional operations. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

Also, the invention is not limited to physical devices or unitsimplemented in non-programmable hardware but can also be applied inprogrammable devices or units able to perform the desired devicefunctions by operating in accordance with suitable program code.Furthermore, the devices may be physically distributed over a number ofapparatuses, while functionally operating as a single device. Also,devices functionally forming separate devices may be integrated in asingle physical device. Other modifications, variations and alternativesare also possible. The specifications and drawings are, accordingly, tobe regarded in an illustrative rather than in a restrictive sense.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The word ‘comprising’ does notexclude the presence of other elements or steps then those listed in aclaim. Furthermore, the terms “a” or “an,” as used herein, are definedas one or more than one. Also, the use of introductory phrases such as“at least one” and “one or more” in the claims should not be construedto imply that the introduction of another claim element by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim element to inventions containing only one suchelement, even when the same claim includes the introductory phrases “oneor more” or “at least one” and indefinite articles such as “a” or “an.”The same holds true for the use of definite articles. Unless statedotherwise, terms such as “first” and “second” are used to arbitrarilydistinguish between the elements such terms describe. Thus, these termsare not necessarily intended to indicate temporal or otherprioritization of such elements. The mere fact that certain measures arerecited in mutually different claims does not indicate that acombination of these measures cannot be used to advantage.

1. An integrated circuit comprising: voltage modulation circuitryarranged to convert an input voltage level at an input node to an outputvoltage level at an output node, the voltage modulation circuitrycomprising a switching element arranged to connect the input node to theoutput node when the switching element is in an ‘ON’ condition, aswitching control module operably coupled to the switching element andarranged to control the connection of the input node to the output nodeby the switching element in accordance with a switching frequency, and afrequency control module operably coupled to the switching controlmodule and arranged to receive an input voltage level indication of theinput voltage level at the input node, and configure the switchingfrequency based at least partly on the input voltage level indication.2. The integrated circuit of claim 1 wherein the frequency controlmodule is further arranged to compare an input reference value based atleast partly on the input voltage level indication to at least onethreshold value to determine an appropriate switching frequency value,and configure the switching frequency in accordance with the determinedswitching frequency value.
 3. The integrated circuit of claim 2 whereinthe frequency control module is further arranged to receive anindication of a load current, and combine the input voltage levelindication and the load current indication to generate the inputreference value.
 4. The integrated circuit of claim 1, wherein thevoltage modulation circuitry further comprises oscillator circuitryarranged to generate a switching frequency signal in accordance with afrequency control signal received from the frequency control module, andto provide the switching frequency signal to the switching controlmodule; and the switching control module is arranged to regulate theconnection of the input node to the output node by the switching elementin accordance with the switching frequency signal.
 5. The integratedcircuit of claim 1, wherein the switching control module is furtherarranged to receive a duty cycle signal; and regulate the connection ofthe input node to the output node by the switching element in accordancewith the duty cycle signal.
 6. The integrated circuit of claim 5,wherein the duty cycle signal is based on a comparison between a loadcurrent indication and a voltage feedback signal fed back from theoutput node.
 7. The integrated circuit of claim 6, wherein the voltagefeedback signal is generated based on a comparison between an indicationof the output voltage level at the output node and a voltage referencesignal.
 8. The integrated circuit of claim 1, wherein the voltagemodulation circuitry comprises a buck converter.
 9. The integratedcircuit of claim 1, wherein the voltage modulation circuitry furthercomprises at least one energy storage component operably coupled betweenthe switching element and the output node, and the at least one energystorage component comprises at least one element selected from the groupconsisting of: an inductor, a transformer and a capacitor.
 10. A voltagemodulation circuitry arranged to convert an input voltage level at aninput node to an output voltage level at an output node, the voltagemodulation circuitry comprising: a switching element arranged to connectthe input node to the output node when the switching element is in an‘ON’ condition; a switching control module operably coupled to theswitching element and arranged to control the connection of the inputnode to the output node by the switching element in accordance with aswitching frequency; and a frequency control module operably coupled tothe switching control module and arranged to receive an indication ofthe input voltage level at the input node, and to configure theswitching frequency based at least partly on the input voltage levelindication.
 11. An electronic system comprising an integrated circuitaccording to claim
 1. 12. The electronic system of claim 11, wherein theelectronic system comprises a single board computer device.
 13. A methodfor converting an input voltage level at an input node to an outputvoltage level at an output node, the method comprising: receiving anindication of the input voltage level at the input node; configuring aswitching frequency based at least partly on the received input voltagelevel indication; and regulating a connection of the input node to theoutput node in accordance with the configured switching frequency. 14.The method of claim 13 further comprising: determining a switchingfrequency value by comparing an input reference value to at least onethreshold value, wherein the input reference value is based at least inpart on the input voltage level indication; and configuring theswitching frequency in accord with the switching frequency value. 15.The method of claim 14 further comprising: receiving an indication of aload current; and generating the input reference value using the inputvoltage level indication and the indication of the load current.
 16. Themethod of claim 13 further comprising: receiving a frequency controlsignal; generating a switching frequency signal in accord with thefrequency control signal; and regulating the connection of the inputnode to the output node in accord with the switching frequency signal.17. The method of claim 13 further comprising: receiving a duty cyclesignal; and regulating the connection of the input node to the outputnode in accord with the duty cycle signal.
 18. The method of claim 17,wherein the duty cycle signal is based on a comparison between a loadcurrent indication and a voltage feedback signal fed back from theoutput node.
 19. The method of claim 18, wherein the voltage feedbacksignal is generated based on a comparison between an indication of theoutput voltage level at the output node and a voltage reference signal.20. The voltage modulation circuitry of claim 10 wherein the frequencycontrol module is further arranged to compare an input reference valuebased at least partly on the input voltage level indication to at leastone threshold value to determine an appropriate switching frequencyvalue, and configure the switching frequency in accordance with thedetermined switching frequency value.